(1) Field of the Invention
The invention relates to processes for packaging integrated circuit dies, and more particularly, to a method of packaging gyroscope sensor modules.
(2) Description of the Related Art
The miniaturization of electronics drives the expansion of product functionality and application. However, the application of the gyroscope (‘gyro’) sensor module has been limited due to the size and weight of the MEMS (Micro Electrical Mechanical Systems) gyro package. Currently, MEMS gyros are available commercially in the form of a package within which the MEMS die 24 is mounted by wire bonding 28, as shown in FIG. 1. For protection the die is contained in an enclosure 20 with a lid 22 which is normally ceramic and/or metallic. On one side of the package, solder ball grid array (BGA) 15 is present to allow the package to be mounted on the main circuit board 10 by solder reflow. Such package design provides a rigid structure to hold the MEMS die, as well as the overall shape of the package allowing it to be handled easily by standard surface mount technology (SMT) processes.
To reduce the spatial requirement of the main circuit board, high density circuitry on multilayer printed circuit boards (PCBs) are available. However, the size of the gyro packages has become a key factor which limits its application in small portable devices, especially when up to three MEMS gyroscopes are required to sense and respond to X-, Y- and Z-axis movements. As demonstrated by J. Barton et al, “Design, Fabrication and Testing of Miniaturized Wireless Inertial Measurement Units (IMU),” IEEE, 2007, a 10 mm SMD IMU sensor could be produced but with little room left for further size reduction due to the large footprint of the gyro packages.
Therefore, the design of gyro sensor modules has been optimized for applications in small, portable devices. By redesigning the MEMS enclosure, the size and thus the weight of the MEMS gyro could be reduced. Consequently, the main circuit board can also reduce in size through the use of a multi-layer flexible substrate and increasing the circuit density. Such smaller, lighter assemblies can be incorporated into a greater variety of portable and mobile devices which opens up opportunities for new applications.
U.S. Pat. No. 6,784,020 (Lee et al), U.S. Pat. No. 8,804,993 (Shulka), U.S. Pat. No. 8,653,642 (Sutanto et al), and U.S. Pat. No. 8,368,154 (Trusov et al) and U.S. Patent Application 2012/0318059 (Otsuki) disclose MEMS devices mounted on flexible substrates.